1. Field of the Invention
The present invention relates to a photoelectric conversion device and a driving method therefor, and more particularly to a photoelectric conversion device provided with a two-dimensional array of reading pixels, adapted for use in a facsimile apparatus, a digital copying apparatus of an X-ray image capture device, and a driving method therefor.
2. Related Background Art
An image reading system utilizing a reduction optical system and a CCD sensor has been conventionally employed for the image capture in the facsimile apparatus, digital copying apparatus or X-ray image capture device, but, based on the recent development of photoelectric semiconductor materials exemplified by hydrogenated amorphous silicon (hereinafter referred to as a-Si), there are conducted active developments for so-called contact sensors having photoelectric converting elements and signal processing units on a large-sized substrate to enable image reading with an optical system of a size same as that of the information source. Particularly a-Si, being usable not only as a-photoelectric converting material but also in a thin film field effect transistor (hereinafter written as TFT), provides an advantage that the photoelectric converting semiconductor layer and the semiconductor layer of TFT can be formed simultaneously.
However, in such photoelectric conversion devices, in case of reading a partial area (hereinafter called trimming operation), it is required to drive all the drive lines or all the pixels to read the outputs of all the pixels and then to extract the signals corresponding to the certain required area. For this reason there is encountered a drawback of requiring time for driving the unnecessary drive lines and time for reading the unnecessary output signals.
In case the photoelectric conversion device is of a large area with pixels of a high definition as in the X-ray image capture device, particularly in case of capturing information of a large number of pixels of a high definition as so-called moving image as in the case of observing the image while irradiating the X-ray image capture device continuously with X-rays, such drawback becomes serious because of the significant signal processing time and also because of the increased X-ray radiation dose in case of the X-ray image capture.
An object of the present invention is to provide a photoelectric conversion device including a two-dimensional array of plural photoelectric converting elements, capable of high-speed signal reading, and a driving method therefor.
Another object of the present invention is to provide a photoelectric conversion device, including an array of plural photoelectric converting elements, not requiring time for driving the unnecessary drive lines and time for reading unnecessary output signals in case of reading the signals of the photoelectric converting elements of a partial area (such reading operation being hereinafter called a trimming operation).
Still another object of the present invention is to provide a photoelectric conversion device enabling image reading with a higher sensitivity, usable as an X-ray image capture device with a reduced X-ray radiation dose, and a drive method therefor.
Still another object of the present invention is to provide a drive method for a photoelectric conversion device in which signals of plural photoelectric converting elements arranged in a two-dimensional array on a substrate are successively read by scanning the drive lines in X-direction in succession and transferring the signal charges in the signal lines in the Y-direction, wherein the signal charge transfer is executed by scanning in succession only arbitrarily selected drive lines among those for the plural photoelectric converting elements, while not driving the remaining drive lines for the signal charge transfer or driving the remaining plural drive lines simultaneously at a timing different from that for the above-mentioned arbitrary drive lines.
Still another object of the present invention is to provide a drive method for such photoelectric conversion device, wherein potentials at both ends of each of the photoelectric converting elements in the remaining drive lines are simultaneously returned to an initial value.
Still another object of the present invention is to provide a drive method for such photoelectric conversion device, wherein such remaining drive lines are driven either collectively or in a divided manner.
Still another object of the present invention is to provide a drive method for such photoelectric conversion device, wherein the drive lines execute a drive for initializing all the photoelectric converting elements after the aforementioned arbitrary drive lines execute transfer of the signal charges obtained by the photoelectric conversion in the corresponding photoelectric converting elements.
Still another object of the present invention is to provide a drive method having a mode for reading the signals by driving the aforementioned arbitrary drive lines and another mode for reading the signals by driving second arbitrary drive lines different from the above-mentioned arbitrary drive lines, and a drive method in which the above-mentioned two modes are executed alternately.
Still another object of the present invention is to provide a drive method wherein the aforementioned arbitrary drive lines are selected in a plural number and such selected drive lines are driven in succession from the innermost one toward the outermost one, and/or the aforementioned arbitrary drive lines are selected in a plural number and a drive is executed for initializing the selected drive lines in succession from the innermost one toward the outermost one prior to the reading of the signal charges by the drive lines.
Still another object of the present invention is to provide a drive method for reading image data from a photoelectric conversion device including a photodetector array consisting of a matrix array of photosensor elements, comprising the steps of:
a) determining, as an object area of the user, an area of the photosensor elements defined by a desired range of rows and a desired range of columns in the photodetector array;
b) detecting the signals of the photosensor elements of at least a row, from the side of one of the mutually opposed edges, in the direction of row, of the object area;
c) detecting the signals of the photosensor elements of at least a row, from the side of the other of the mutually opposed edges, in the direction of row, of the object area; and
d) alternately repeating the steps b) and c), except for the already detected rows, until the signals of the photosensor elements of the row at the central portion of the object area are detected.
Still another object of the present invention is to provide a drive method for reading image data from a photoelectric conversion device including a photodetector array consisting of a matrix array of photosensor elements, comprising the steps of:
a) determining, as an object area of the user, an area of the photosensor elements defined by a desired range of rows and a desired range of columns in the photodetector array;
b) detecting signals of the photosensor elements of at least a row in a central portion of the object area;
c) detecting signals of the photosensor elements of at least a row adjacent to one of the two sides of the already detected row;
d) detecting signals of the photosensor elements of at least a row adjacent to the other of the two sides of the already detected row; and
e) alternately repeating the steps of c) and d), except for the already detected rows, until the signals of the photosensor elements of the rows on the mutually opposed edges, in the direction of row, of the object area are detected.
Still another object of the present invention is to provide a drive method for driving a photoelectric conversion device which is provided with a photodetector array consisting of a matrix array of photosensor elements and in which signals from at least a part of the photosensor elements of each column are taken out from a common column output line through switching elements, comprising the steps of:
a) determining, as an object area of the user, an area of the photosensor elements defined by a desired range of rows and a desired range of columns in the. photodetector array;
b) taking out the signals to the column output line by driving a switch element corresponding to the photosensor elements of at least a row, from the side of one of the mutually opposed edges, in the direction of row, of the object area;
c) taking out the signals to the column output line by driving a switch element corresponding to the photosensor elements of at least a row, from the side of the other of the mutually opposed edges, in the direction of row, of the object area; and
d) alternately repeating the steps b) and c), except for the already detected rows, until the signals of the photosensor elements of the row at the central portion of the object area are detected.
Still another object of the present invention is to provide a drive method for driving a photoelectric conversion device which is provided with a photodetector array consisting of a matrix array of photosensor elements and in which signals from at least a part of the photosensor elements of each column are taken out from a common column output line through switching elements, comprising the steps of:
a) determining, as an object area of the user, an area of the photosensor elements defined by a desired range of rows and a desired range of columns in the photodetector array;
b) taking out the signals to the column output line by driving a switch element corresponding to the photosensor elements of at least a row at the central portion of the object area;
c) taking out the signals to the column output line by driving a switch element corresponding to the photosensor elements of at least a row adjacent to one of the side of the already detected row;
d) taking out the signals to the column output line by driving a switch element corresponding to the photosensor elements of at least a row adjacent to the other of the side of the already detected row; and
e) alternately repeating the steps c) and d), except for the already detected rows, until the switch elements corresponding to the photosensor elements of the rows at the mutually opposed edges, in the direction of row, of the object area are driven.
Still another object of the present invention is to provide a photoelectric conversion device provided with a photodetector array composed of a matrix array of photosensor elements and including a signal charge accumulation unit corresponding to each photosensor element and a switch unit provided in the signal output path from such signal charge accumulation unit, the device comprising:
object area determination means for determining, as an object area of the user, an area of the photosensor elements defined by a desired range of rows and a desired range of columns in the photodetector array, and drive means for generating a drive signal for the photodetector array based on the output of the object area determination means;
wherein the drive means is adapted to generate the drive signal for the photodetector array in such a manner as to reset the charges of the signal charge accumulation units by driving the switch units of the photodetector array in succession from a row at the periphery of the object area to a row at the center thereof, and, after the exposure to the light, to read the signal charges of the signal charge accumulation units by driving the switch units of the photodetector array in succession from the central portion of the object area to the peripheral portion thereof.
Still another object of the present invention is to provide a photoelectric conversion device comprising read instruction detecting means for detecting a read instruction, and control means for controlling the aforementioned drive means based on the output of the read instruction detecting means, wherein the control means is adapted to effect the resetting, the exposure after the resetting and the signal charge reading after the exposure based on the output of the read instruction detecting means, and to provide a photoelectric conversion device further comprising conversion means for converting an X-ray, emitted from X-ray irradiation means, into a visible light, and adapted to detect the visible light, emitted from the conversion means, by the photodetector array.
Still another object of the present invention is to provide a photoelectric conversion device, wherein the drive means is adapted to generate drive signals for the photodetector array, in such a manner as to refresh the signal charge accumulation units by driving the switch units of the photodetector array in succession from a row in the peripheral portion of the object area to a row at the central portion thereof.
Still another object of the present invention is to provide a photoelectric conversion device for reading the signals in succession from plural photoelectric converting elements arranged two-dimensionally on a substrate, by scanning the drive lines of the X-direction in succession thereby transferring the signal charges in the Y-direction, comprising means for successively scanning the arbitrary drive lines only of the above-mentioned plural photoelectric converting elements.
Still another object of the present invention is to provide such photoelectric conversion device comprising means for simultaneously driving the remaining drive lines at a timing different from the drive timing for the above-mentioned arbitrary drive lines.